Embodiments in accordance with the present invention relate to a method for producing a thin film magnetic head to be used for a disk storage unit.
Recently, a capacity of a disk storage unit used as an external storage of a computer has been increased, and a recording density of the same has been increased year by year. Briefly speaking, the disk storage unit is formed of a magnetic disk and a magnetic head. The magnetic head is provided with an inductive magnetic exchange element (inductive element) serving as a write element and a giant magnetoresistive (GMR) element serving as a read element. In order to realize the high recording density, it is necessary to downsize the read element and the write element as well as to decrease the size of 1 bit on the magnetic disk. Therefore, in order to achieve the high recording density, the element sizes are reduced year by year, particularly, the size of the GMR element serving as the read element has been reduced to the order of submicron. With the reduction in the element size described above, electrical strength for electrical damages such as ESD (ElectroStatic Discharge) and EOS (Electrical OverStress) on the GMR element is reduced to raise problems such as hard ESD that causes the GMR element to be melted due to an overcurrent in the magnetic head production process and soft ESD that deteriorates magnetic properties.
[Patent Publication 1] JP-A-09-44820
[Patent Publication 2] JP-A-11-296817
[Patent Publication 3] JP-A-10-241124
[Patent Publication 4] JP-A-2003-6816
In conventional technologies, for the purpose of preventing the damage due to ESD from being inflicted on the GMR element, a condenser, for example, is incorporated into the magnetic head to prevent the overcurrent from flowing to the GMR element as disclosed in Patent Publication 1 and Patent Publication 2. Further, a method of recovering the magnetic properties of the magnetic head deteriorated due to the soft ESD by supplying a direct current to the GMR element and a method of recovering by a pulse current and a static magnetic field are disclosed in Patent Publication 3 and Patent Publication 4.
As described in the foregoing, one of means for achieving the high recording density of the disk storage unit is to reduce the element size of the magnetic head and to reduce the size of 1 bit to be recorded on the magnetic disk. However, along with the reduction in element size, the voltage strength for ESD (Electrostatic Discharge) is reduced to cause a defect of melting of GMR due to the overcurrent and a defect of deterioration in magnetic properties. Particularly, in regards to the soft ESD that deteriorates the magnetic properties, it has not been clarified by now in which one of process steps of the production process and by what cause the soft ESD occurs. Therefore, methods of previously incorporating a protection circuit for ESD or of recovering a magnetic head whose properties are deteriorated have heretofore been employed. However, these technologies have the following problems.
For example, in the method of preventing the overcurrent from flowing to the GMR element by incorporating a condenser into the magnetic head, it is necessary to suppress increases in production process and production cost due to addition of a process of producing the condenser. Also, since the magnetic head having the condenser is ultimately incorporated into a disk storage unit, it is necessary to prevent frequency properties from being deteriorated in a disk storage unit handling a high frequency signal.
In turn, in the method of recovering the magnetic properties of the magnetic head with the use of the direct current and the pulse current, due to the necessity of adding a process of property recovery, it is necessary to suppress increases in production process and production cost. Also, though the deterioration in magnetic properties is judged from a degree of a change in resistance of the GMR element measured by applying an alternating magnetic filed to the magnetic head, the magnetic field used in the conventional technology is insufficient for correctly judge the magnetic properties deterioration in view of the fact that a remarkably large magnetic field is required for correctly determine the deterioration in magnetic properties, and it is probable that a very small deterioration is missed by such judgment.
An object of this invention is to provide a method for producing a thin film magnetic head, which enables to solve the above-described problems and to suppress deterioration in magnetic properties of a read element during a production process without increasing a production process and a production cost.